JPH1092731A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve alignment accuracy of an original plate and a substrate of a step-and-scan projection aligner by correcting position measurement results obtained by an alignment system for measuring the position of the original plate and the substrate, corresponding to the position of an original plate stage. SOLUTION: The position of a stage 531 is measured by a laser interferometer and an encoder. Alignment measuring means 52 corrects a measurement value 521 obtained by a sensor and each scope, using a correction value from an interpolation processing unit 51. The corrected value is reduced to an alignment value of each stage by an alignment value processing unit 522. This alignment value is inputted to a stage position processing unit 534 of stage positioning means 53. The stage position processing unit 534 calculates a positioning target value 533 of each stage, on the basis of the alignment value and a stage position measurement value 532, and supplies the calculated value to a driving system of the stage 531. The driving system of the stage 531 positions each stage on the basis of the target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an exposure apparatus used for manufacturing a semiconductor device or the like by exposing a design pattern on a resist on a substrate and a device manufacturing method using the same.

[0002]

2. Description of the Related Art In a one-shot exposure type exposure apparatus, when a projection optical system is constituted by a lens, an image forming area has a circular shape. However, since the semiconductor integrated circuit generally has a rectangular shape, the transfer area in the case of batch exposure is a rectangular area inscribed in a circular imaging area of the projection optical system. Therefore, even the largest transfer area has a diameter of 1 /
正方形 2 is a square with sides. On the other hand, the transfer area is enlarged by scanning and moving the reticle and wafer synchronously using a slit-shaped exposure area having a diameter approximately equal to that of the circular imaging area of the projection optical system. A scanning exposure method (step and scan method) has been proposed. In this method, when a projection optical system having an imaging area of the same size is used, a larger transfer area is secured as compared with the step-and-repeat method in which collective exposure is performed for each transfer area using a projection lens. be able to. That is, since there is no restriction by the optical system in the scanning direction, it is possible to secure only the stroke of the scanning stage, and it is possible to secure approximately √2 times the transfer area in the direction perpendicular to the scanning direction. .

An exposure apparatus for manufacturing a semiconductor integrated circuit is required to have an enlarged transfer area and an improved resolution in order to cope with the manufacture of a chip having a high degree of integration. The adoption of a smaller projection optical system is advantageous from the viewpoint of optical performance and cost, and the step-and-scan type exposure apparatus has been attracting attention as a mainstream of the exposure apparatus in the future.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the performance of a projection exposure apparatus, particularly, a step-and-scan type projection exposure apparatus, especially the alignment accuracy of an original plate and a substrate.

[0005]

According to the present invention, there is provided an illumination optical system for illuminating a predetermined illumination area on an original, and a projection for projecting an original pattern in the illumination area onto a substrate. An optical system, an original stage capable of moving the original in a predetermined direction with respect to the illumination area, a substrate stage capable of moving the substrate in a predetermined direction with respect to a projection area conjugate to the illumination area, An alignment system for measuring the positions of the original and the substrate, and projecting the pattern on the original onto the substrate by scanning the original and the substrate together perpendicularly to the optical axis of the projection optical system. In the exposure apparatus, there is provided means for correcting the position measurement result by the alignment system in accordance with the position of the original stage.

In a preferred embodiment of the present invention, the correction means has means for calculating a correction value of the detection result of the positional deviation by an operation using the original stage position as a variable. Further, as the alignment system, an off-axis alignment system for measuring the position of the substrate in off-axis, a non-exposure light TTL alignment system for measuring the position of the substrate with predetermined non-exposure light via the projection optical system,
Exposure for measuring a shift between a first reference mark provided on the original stage and a second reference mark provided on the substrate stage with a light flux having substantially the same wavelength as exposure light via the projection optical system. An optical TTR alignment system, an original alignment system for measuring a deviation between a pattern on the original and a third reference mark provided on the original stage, and a focus detection system for measuring a position of a pattern surface of the substrate. Examples can be given. The original stage is supported by an original stage base, and the original stage base and the alignment system are supported by a projection optical system base supporting a lens barrel of a projection optical system. Off-axis alignment system, non-exposure light TT
The L alignment system and the focus detection system measure the position of the substrate or the substrate surface with reference to the lens barrel of the projection optical system.
More preferably, the alignment system detects the displacement while the original stage is positioned at a predetermined position.

[0007]

[Operation and Effect] In a projection exposure apparatus, a lens barrel base supporting a lens barrel of a projection optical system is generally used as an apparatus reference.
An alignment system for aligning the original and the substrate is also attached to the lens barrel base. The present inventors have found that this lens barrel base plate is deformed by an eccentric load and a reaction force at the time of acceleration / deceleration when the original stage moves, and such deformation causes exposure accuracy such as overlay accuracy and focus accuracy of the exposure apparatus. The present invention has been found to have a non-negligible effect on the above and that the above deformation depends on the position of the original stage.

According to the present invention, in the alignment system for aligning the original and the substrate, the alignment measurement values of the original and the substrate are corrected in accordance with the original stage position. Accuracy degradation can be reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a scanning exposure apparatus according to one embodiment of the present invention. This apparatus projects a part of the reticle pattern onto a wafer in a slit shape via a projection optical system, and scans the reticle pattern relative to the projection optical system by synchronizing the reticle and the wafer together. This is a step-and-scan type exposure apparatus that exposes a wafer and performs this scanning exposure on a plurality of transfer regions (shots) on the wafer while interposing a step movement for repeating the exposure. In FIG. 1, an illumination optical system 1 illuminates a predetermined area on a reticle 2 held by a reticle stage 11 in a slit shape. Reference numeral 3 denotes a projection optical system which projects a pattern of a region illuminated by the illumination optical system 1 on the reticle 2 onto the wafer 6 held on the wafer stage 5 at a predetermined reduction magnification.

The reticle stage 11 is driven in the X direction by a linear motor (not shown), and the wafer stage 5 is driven in the X and Y directions by an X direction linear motor and a Y direction linear motor (not shown). The synchronous scanning of the reticle 2 and the wafer 6 is performed by moving the reticle stage 11 and the wafer stage 5 in a direction opposite to each other in the X direction at a constant speed ratio (for example, 4: 1). A Z-tilt stage (not shown) is mounted on the wafer stage 5, and a wafer chuck (not shown) for holding a wafer is mounted thereon.

The wafer stage 5 is a wafer stage base 1
9, reticle stage 11 is provided on reticle stage surface plate 27, and reticle stage surface plate 2
The projection optical system 7 and the projection optical system 3 are provided on a lens barrel base 10. The stage base 19 and the barrel base 10 are supported on the base frame 17 at three points via three dampers 18. The damper 18 is an active damper for actively damping or removing vibration in six axial directions, but a passive damper may be used.

Reference numerals 7 and 8 denote laser interferometers for measuring the positions of the reticle stage 11 and the wafer stage 5 with reference to the lens barrel. The measurement values of the laser interferometers 7 and 8 are sent to a control device (not shown) together with the measurement values (alignment values) of the scopes 12, 14, 15, and 16 described later, and the control device performs a reticle based on these measurement values. The stage 11 and the wafer stage 5 are driven to perform positioning such as step movement and synchronous scanning of the reticle 2 and the wafer 6.

The light projecting means 9a and the light receiving means 9b constitute a focus sensor for detecting whether or not the wafer 6 on the wafer stage 5 is located on the focus surface of the projection optical system 3. That is, light is radiated to the wafer 6 from an oblique direction by the light projecting means 9a fixed to the lens barrel base 10, and the position of the reflected light is detected by the light receiving means 9b, whereby the optical axis of the projection optical system 3 is detected. The position of the surface of the wafer 6 in the direction is detected. The light projecting means 9a has a light emitting element such as an LED, and the light receiving means 9b has a light receiving element such as a CCD sensor.

Reference numeral 12 denotes exposure light or light having substantially the same wavelength as the exposure light. The reticle 2 or the first reference plate 4 on the reticle stage 11 and the wafer 6 or the second reference plate on the wafer stage 5 via the projection optical system 3. 13 is an exposure light TTR scope capable of observing at the same time. The first reference plate 4 is fixed near both ends in the X direction of the reticle stage 11 so that at least one of the first reference plates 4 comes into the slit-shaped illumination area of the illumination optical system 1 when the reticle stage 11 comes to the reticle exchange position. I have. Second reference plate 13
Is fixed at a position on the wafer stage 5 which does not interfere with the wafer 6.

Reference numeral 14 denotes a reticle exchange position, and an FRA (fine reticle alignment) scope for detecting a relative positional shift between a reticle 2 and a reticle reference plate (not shown) fixed to the reticle stage 11; This is a non-exposure light TTL scope for measuring the positional deviation of the wafer 6 with respect to the reference of the wafer 6 using the non-exposure light via the projection optical system 2. A correction optical system (not shown) for correcting the aberration between the exposure light and the non-exposure light in the projection optical system 3 is provided in the optical path of the non-exposure light TTL scope 15.
Further, a prism (not shown) is provided for inputting non-exposure light to the projection optical system 3 from the scope 15 side and extracting reflected light from the wafer 6 from the projection optical system 3.

Reference numeral 16 denotes a wafer 6 with respect to its own reference.
Is an off-axis scope for measuring the positional deviation of the projection optical system 3 outside the field of view. Reference numeral 34 denotes a blade stage for scanning a light-shielding blade for restricting an illumination light beam so as not to expose a shot other than an exposure target shot during the acceleration / deceleration of the reticle stage 11 before and after the scanning exposure and the idle running period. The position of the blade stage 34 is constantly measured by an encoder (not shown), and is scanned in synchronization with the reticle stage 11 at least immediately before and immediately after the start and end of the scanning exposure.

In this configuration, the wafer 6 is loaded onto the wafer stage 5 from the front of the apparatus (on the front side of FIG. 1) by the transfer means (not shown), and when predetermined alignment is completed, the exposure apparatus performs scanning exposure and The pattern of the reticle 2 is exposed and transferred to a plurality of transfer areas on the wafer 6 while repeating the step movement. At the time of scanning exposure, the reticle stage 11 and the wafer stage 5 are moved at a predetermined speed ratio in the X direction (scanning direction) to scan the pattern on the reticle 2 with slit-like exposure light, and to project the wafer on the projected image. By scanning 6, a pattern on the reticle 2 is exposed to a predetermined transfer area on the wafer 6. During the scanning exposure, the height of the wafer surface is measured by the focus sensor 9 (9a, 9b), and the height and tilt of the wafer stage 5 are controlled in real time based on the measured values, thereby performing focus correction. When the scanning exposure for one transfer area is completed, the wafer stage 5 is driven to move the wafer stepwise in the X direction and / or the Y direction, thereby positioning the other transfer area with respect to the start position of the scanning exposure. A scanning exposure is performed. Note that a combination of the step movement in the X and Y directions and the movement for scanning exposure in the X direction allows each of the plurality of transfer areas on the wafer to be sequentially and efficiently exposed. The arrangement of the transfer area, the scanning direction of either positive or negative Y, the order of exposure to each transfer area, and the like are set.

FIG. 2 is a block diagram showing a control system of the apparatus shown in FIG. In the figure, 51 is an alignment value correcting means, 52 is an alignment measuring means, and 53 is a stage positioning means. The stage 531 in the stage positioning means 53 corresponds to the reticle stage 11, the wafer stage 5, the blade stage 34 and their driving systems in FIG. 1, and the measured stage position 532 is the laser interferometers 7 and 8 in FIG. Corresponds to the measured value of The alignment measurement value 521 in the alignment measuring means 52 is the focus sensor 9 and the scope 1 shown in FIG.
2, 14, 15, and 16 are measured values. The alignment value correction means 51 stores the relationship between the position of the reticle stage 11 and the correction value of the measurement value by each of the scopes 12, 14, 15, and 16 as an AA correction value table 511 or a correction function. Such a correction value may be determined in advance by measuring errors at a plurality of positions on the reticle stage 11 using a reference reticle or a reference wafer, and based on the errors.

The position of the stage 531 is determined by the laser interferometer 7,
8 and the measured value 5
32 is input to the stage position calculator 534. Also,
The measurement value of the interferometer 7 is also input to a comparator 512 in the alignment value correction means 51. The comparator 511 reads the correction value of the position of the reticle stage 11 indicated by the measurement value of the interferometer 7 or a position near the reticle stage 11 for each sensor 9 and each scope. The interpolation calculator 513 calculates a correction value for each scope and sensor when the reticle stage 11 is at the current position, based on these correction values. The alignment measuring means 52 corrects the measurement value 521 by the sensor 9 and each scope by the correction value from the interpolation calculator 513, and converts it into the alignment value of each stage 11, 5, 34 by the alignment value calculator 522. This alignment value is input to the stage position calculator 534 of the stage positioning means 53. Stage position calculator 53
4 is the alignment value and the stage position measurement value 53
Then, a target position value 533 for each stage is calculated based on 2 and given to the drive system of the stage 531. Stage 53
In the drive system 1, each stage 11,
Position 5,34.

In this manner, the focus sensor 9 and the scopes 12, which are caused by the deformation of the lens barrel base 10 due to the eccentric load when the reticle stage 11 moves and the reaction force during acceleration / deceleration,
It is possible to correct errors in the alignment measurement values of 14, 15, and 16 and to minimize the deterioration of the alignment measurement accuracy. In this case, alignment accuracy can be further improved by positioning each stage at a fixed position as much as possible and performing alignment measurement. For example, the alignment measurement by the off-axis scope 16 and the non-exposure light TTL scope 15 is performed in a state where the reticle stage 11 is located at the reticle exchange position or the exposure standby position of the first shot, and the blade stage 34 is located at the exposure standby position of the first shot. The measurement by the FRA scope 14 may be performed with the reticle stage 11 at the reticle exchange position or the first shot exposure standby position and the wafer stage and the blade stage 34 at the first shot exposure standby position.

In the above description, an example has been described in which the deformation of the lens barrel base 10 due to the movement of the reticle stage 11 and the fluctuation of the alignment measurement value due to the deformation are corrected. Can be performed.

FIG. 3 shows a reticle or wafer alignment operation in the apparatus shown in FIG. During alignment,
First, a stage on which an alignment target (wafer and / or reticle) is mounted is moved to an alignment measurement position. Next, alignment measurement is performed using an alignment scope. At the same time, an alignment correction value based on the stage position is calculated. An alignment value is calculated based on the alignment measurement value and the alignment correction value. Subsequently, it is determined whether or not the alignment has been completed. If the alignment has not been completed, the above operation is repeated for the next alignment measurement position. Calculation of a stage target value based on the stage position and the alignment value is performed in parallel with the determination of the end of alignment. Run.

The measurement values of the focus sensor 9 for performing the focus correction during the scanning exposure and the measurement values for scanning the blade stage 34 are the same as those described above, except that they are executed during the scanning exposure. To correct the measured value.

[0024] Example 4 of the manufacturing of the micro device microdevices (IC or LSI, etc. of the semiconductor chip,
2 shows a flow of manufacturing a liquid crystal panel, a CCD, a thin-film magnetic head, a micromachine, and the like. In step 1 (circuit design), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. Step 6
In (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 5 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device, which has been conventionally difficult to manufacture, at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an alignment value correction system in the exposure apparatus of FIG.

FIG. 3 is a diagram showing a flow of an alignment measurement sequence of the apparatus of FIG. 1;

FIG. 4 is a diagram showing a flow of manufacturing a micro device.

FIG. 5 is a diagram showing a detailed flow of a wafer process in FIG. 4;

[Explanation of symbols]

1: illumination optical system, 2: reticle, 3: projection optical system, 4:
First reference plate, 5: wafer stage, 6: wafer,
7, 8: laser interferometer, 9 (9a, 9b): focus sensor, 10: lens barrel base, 11: reticle stage, 1
2: exposure light TTR scope, 13: second reference plate,
14: FRA (fine reticle alignment) scope, 15: non-exposure light TTL scope, 16: off-axis scope, 17: base frame, 18: damper, 1
9: wafer stage base, 27: reticle stage base, 34: blade stage, 51: alignment value correction means, 511: AA correction value table, 512: comparator, 513: interpolation calculator, 52: alignment measurement means, 521: alignment measurement value, 522: alignment value calculator, 53: stage positioning means, 531: stage, 532: stage position measurement value, 533: stage target value, 534: stage position calculator.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/30 525J 525K 526B

Claims (7)

[Claims] 1. An illumination optical system for illuminating a predetermined illumination area on an original, a projection optical system for projecting a pattern on the original in the illumination area onto a substrate, and a direction of the original relative to the illumination area in a predetermined direction. An original stage that can be moved to, a substrate stage that can move the substrate in a predetermined direction with respect to a projection area conjugate to the illumination area, and an alignment system that measures the positions of the original and the substrate, A projection exposure apparatus that scans the original and the substrate together perpendicularly to the optical axis of the projection optical system and sequentially projects a pattern on the original onto the substrate, wherein the position measurement result by the alignment system is used as the original stage. A projection exposure apparatus provided with a means for correcting in accordance with the position. 2. The projection exposure apparatus according to claim 1, wherein said correction means includes means for calculating a correction value of the position shift detection result by an operation using the original stage position as a variable. 3. The projection exposure apparatus according to claim 1, wherein the alignment system detects the displacement while the original stage is positioned at a predetermined position. 4. An off-axis alignment system for measuring the position of the substrate with off-axis, and a non-exposure light TTL alignment for measuring the position of the substrate with predetermined non-exposure light via the projection optical system. System, and measures a deviation between a first reference mark provided on the original stage and a second reference mark provided on the substrate stage with a light flux having substantially the same wavelength as exposure light via the projection optical system. An exposure light TTR alignment system, an original alignment system for measuring a deviation between a pattern on the original and a third reference mark provided on the original stage, and a focus detection system for measuring a position of a pattern surface of the substrate 2. The method according to claim 1, further comprising at least one of the following.
4. The projection exposure apparatus according to any one of claims 1 to 3. 5. The projection exposure apparatus according to claim 4, wherein the off-axis alignment system, the non-exposure light TTL alignment system, and the focus detection system perform measurement based on a barrel of the projection optical system. 6. The original stage is supported by an original stage base, and the original stage base and the alignment system are supported by a projection optical system base supporting a barrel of the projection optical system. The projection exposure apparatus according to claim 1, wherein: 7. A device manufacturing method using the apparatus according to claim 1.